1. Field of the Invention
The present invention relates to a bottom substrate for liquid crystal display device and the method for manufacturing the same, more particularly, to a bottom substrate for reflective liquid crystal display device and method for manufacturing the reflective or transflective liquid crystal display device.
2. Description of Related Art
Currently, the demand for dealing with the brightness problem of liquid crystal display exists since various liquid crystal displays and their related products appear in the market. Half of the present liquid crystal displays on the market consume huge energy or power in backlight module. Therefore, in order to solve brightness and power consumption problem, some researchers suggest to use the ambient light of the environment around displays. The suggested design does not only extend the lifetime of battery but also reduce the weight of the LCD device. In addition, the demand for transflective liquid crystal display designed for portable products such as cellular phones or PDA has increased recently. However, the technical requirement of the transflective liquid crystal display becomes more complicated than that of the transparent liquid crystal display.
It is known that a transflective display device has combined advantages of transparent displays and reflective displays. Actually, this kind of apparatus is provided with partially reflective medium. The partially reflective medium is like back flapping media of mirror, which allows the light from backlight module to pass by. At the same time, the light from the front side of the display can be reflected back and pass through the liquid crystal display (LCD) panel to enhance the brightness of the back light module. The manufacturer in this field is still seeking for better methods for manufacturing transflective display, which can provide more reflective light. It is not only viewable under sunlight, but allowed enough light from backlight module passing through; therefore, the display can be able to use indoor or overcast daytime.
According to the conventional preparing method of reflective layer, steps of forming a metal layer, which is provided with reflective properties, on the completed pixel electrode of thin film transistor (TFT) array is very common. Moreover, steps of forming bumps on the metal layer or on the pixel electrode, then forming a metal layer of reflective property in order to increase refractive index are also popular in the manufacturing process.
Most of the methods of prior arts for forming protrusions on the bottom substrate for a LCD panel are achieved though exposures, developing and etching. For instance, a method for manufacturing a rugged surface by several exposure, development and etching steps is disclosed in U.S. Pat. No. 6,600,535, as shown in FIG. 1A to FIG. 1M. However, the declined angle of each protrusion on the rugged surface made by the method disclosed in U.S. Pat. No. 6,600,535 is difficult to control. Moreover, the distance between adjacent protrusions cannot be easily controlled either since the distance between adjacent protrusions are easily effected by the conditions of exposures. Furthermore, the adjustment of the conditions or the sequence of steps of the conventional process for manufacturing the protrusions is also difficult. Hence, only rugged surface with regular protrusions is frequently made in convenience. The irregular protrusions can't be prepared easily by the conventional methods with steps of exposure, development, and etching. Owing to this reason, the reflective effect is limited.
Therefore, it is desirable to provide an improved method or device to mitigate and/or obviate the aforementioned problems.